Period 1894-1910
Documents received by Marsh mainly as editor of and given by him to Max Nettlau in 1904: letters from Petr A. Kropotkin 1894-1910, Sofija (Sophie) Kropotkin 1896-1904, Charlotte M. Wilson 1895-1901 and some others; manuscripts of articles and notes by Petr A. Kropotkin and others.

Period 1880-1894
Documents relating to the British, Continental and General Federation for the Abolition of the State Regulation of Vice and the Deutsche Kulturbund: letters, circulars, `report from Germany', statutes, notes, copies of articles, translations of pamphlets and articles by Josephine Butler and others,...

Period 1910-1935
Part of his papers: correspondence with publishers, literary agents and translators, the BBC, the Society of Authors, Playwrights and Composers, etc. 1910-1935, 1944-1957; letters received in reaction to his articles promoting the World Socialist Movement 1954-1956; typed and handwritten manuscripts...